This invention relates to an improved combination of basic fluid logic elements which provide complex, but well known logic functions. Specifically, a combination of two or three logic elements, i.e. a flip-flop element plus one or two sequential AND elements or sequential NOT elements, provide the binary flip-flop, shift register or staging functions. These combinations are useful in pneumatically controlled environments such as with assembly lines and other manufacturing processes.
Shift Register Control
Conveyor and sorting operations in manufacturing processes require escort memory functions. For example, certain attributes of an object, such as size, shape, and weight may be sensed at one point in a production line and then acted upon when the object has moved further down the line. To accomplish this escort function, the signal generated at the sensing station must be memorized and then escort the object to the station where action is to take place. There the signal is used to initiate a task such as automatic sorting, rejecting or positioning.
It is known that the control requirements of the escort memory function can be implemented with a shift register control. Such a control provides that a signal generated at a sensing station will be passed to a first stage operation by a shift signal pulse. A second shift signal will then pass the sensing station signal to a second stage and so on. The number of shift register stages is equal to the number of objects between the sensing station and the station where a corresponding action is to take place.
Flip-flop elements can be used as basic building blocks for a shift register control since multiple memory functions are required. Heretofore, a considerable amount of additional control elements and other hardware were necessary to build a fluid or pneumatic shift register control using flip-flop elements. This made implementation of a fluid logic shift register control system complex, expensive and generally impractical. Elimination of excess hardware associated with such a fluid shift register control system is therefore considered desirable.
Binary Flip-Flop Control
Another complex control system is known as the binary flip-flop control. Such a control is functionally known and its uses are also known. However, all known systems of binary flip-flop control using fluid or pneumatic elements are complex and require many logic elements. As a consequence, production of a pneumatic binary flip-flop control has heretofore been uneconomical.
Staging Controls
Sequential pneumatic logic control systems constructed with the flip-flop elements have been built and sold for several years. Typically these systems employ staging circuits where each of the flip-flop elements is controlled by a separate input.
Some pneumatic control applications, however, require that the control sequence of a staging circuit advance step-by-step with pressure pulses generated from a single signal source. To provide this type of pneumatic control, it has been necessary to build special cam driven programmers containing a series of mechanically actuated pneumatic valves. Mechanical programmers of the described type have limitations in versatality and may not be adaptable to differing requirements, such as variance of the number of steps per cycle. Heretofore no satisfactory mechanism or system is known to provide complex pneumatic staging circuits which would operate from a single signal source.